1. Field of the Invention
The present invention relates to an image processing apparatus provided with a digital data processing apparatus.
2. Description of the Prior Art
In a complicated apparatus such as copying machine there are provided a plural number of circuits. Many signals are transmitted to and from the circuits. For such apparatus, it is a common practice in the art to allot one signal line to one operation. Therefore, the number of signal lines required increases with increasing the complexity of operations then required. Increase of the number of signal lines makes complicated the wirings between circuits as well as the structure of interface circuits. The problems of high cost and low reliability are caused thereby.
To decrease the number of signal lines necessary between circuits, it has already been proposed and practically accepted to use a signal coding circuit at the signal output side and a signal decoding circuit at the signal input side. However, it has been found that this solution also has many drawbacks. As coding and decoding circuits are required, it also makes the circuits of the apparatus complicated so much. When man wishes to modify the specification of signals used in the apparatus, it is required to change the circuit completely. This is time and labour consuming.
Furthermore, to conduct adjustment and inspection of every unit circuit, the signal lines between the circuits have to be removed and also a particular signals has to be externally introduced into the circuit to prevent any malfunction of the circuit during the adjustment and inspection. Therefore, the service man who has a charge of such apparatus in the market has been compelled to consume a long time and a great labour for adjustment and inspection.